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#73855 - 03/09/08 11:45 am Another " dumbest " question......  
Joined: Aug 2006
Posts: 730
johnnyrvf Offline
BritBike Forum member
johnnyrvf  Offline
BritBike Forum member

Joined: Aug 2006
Posts: 730
Dordogne, SW France
confused : Whilst I can get my head around most things , HRC V4 valve timing , Triumph Trident primary transmissions etc , I am having a problem undestanding Norton Isolastics ; Can somebody please explain to me EXACTLY what the 2 smaller rubbers secured by the circlips ; the ' Engine Mounting Buffers ' on the Engine Mounting Spacer as named in the parts manual in the middle of the Engine mounting bracket do? and how? they just appear to take up space for no reason....????? confused Johnny


What d'ya mean it won't rev to 10?
1965 BSA A65D Lightning Rocket
1976 K*w*s*ki Z900.
1978 Triumph Bonn3ville (930 T160 Powered T140)
1988 H*nd* RC30
1990 Moto Guzzi California 3
1993 Y*m*h* TDM 850
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#73856 - 03/09/08 1:43 pm Re: Another " dumbest " question......  
Joined: Sep 2006
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MexicoMike Offline
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MexicoMike  Offline
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Joined: Sep 2006
Posts: 609
Mexico City, Mexico
Actually, they don't do anything!

They were left over parts from Norton's abortive attempt to manufacture garden watering hose. It was unsuccessful because the prototype hose leaked where it was joined to the fittings despite every type of connection and/or sealer that was tried.

Management decreed that the prototype had to be used for something as opposed to destroyed, for fear of the bad publicity that would occur if the media learned of the failure/destruction.

One of the shop stewards received a cash award when he proposed a scheme whereby the hose was cut into thousands of small rings and inserted into the Isolastic units. All the hose was used in this way since it effectively disposed of the hose, did not adversely affect the use of the motorcycle, and could not be seen in normal operation.


OK, OK, I have no Idea about the real answer to the question but doesn't the above sound like it COULD be true! smile

#73857 - 03/09/08 4:26 pm Re: Another " dumbest " question......  
Joined: Aug 2001
Posts: 1,253
Dave Comeau Offline
Crew Chief
Dave Comeau  Offline

Crew Chief

Joined: Aug 2001
Posts: 1,253
Hamilton, Mass. USA
The bigger rubbers support the normal position of the drive train components. They allow for a softer deflection rate for cruising conditions and single weigh load. Therefore a more generous movement is allowed.
The secondary buffers are to create a stiffer deflection rate for the kiddies doing hole shots. Upon a much higher load the secondary rubbers make contact and severly reduce physical deflection.
This can also be noticed if you try and use the commando as a pickup truck to carry your camping stuff or a heavy passenger... you WILL bottom out the conventional 1st buffer and people of average awareness will definitely notice the huge increase in vibration being transmitted to the frame. You are now running on BOTH rubbers...the big diameter ones and the small diameter buffers
bigt


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
#73858 - 03/09/08 6:37 pm Re: Another " dumbest " question......  
Joined: Oct 2007
Posts: 159
79x100 Offline
BritBike Forum member
79x100  Offline
BritBike Forum member

Joined: Oct 2007
Posts: 159
Belgium
Quote:
Originally posted by Dave Comeau:
The bigger rubbers support the normal position of the drive train components. They allow for a softer deflection rate for cruising conditions and single weigh load. Therefore a more generous movement is allowed.
The secondary buffers are to create a stiffer deflection rate for the kiddies doing hole shots. Upon a much higher load the secondary rubbers make contact and severly reduce physical deflection.
This can also be noticed if you try and use the commando as a pickup truck to carry your camping stuff or a heavy passenger... you WILL bottom out the conventional 1st buffer and people of average awareness will definitely notice the huge increase in vibration being transmitted to the frame. You are now running on BOTH rubbers...the big diameter ones and the small diameter buffers
bigt
So Commandos are designed not to carry overweight passengers ? Good job that Harley and Honda's Gold Wing have got that segment tied up then ! bigt


'39 WD16H
'75 850 Commando
#73859 - 03/09/08 8:32 pm Re: Another " dumbest " question......  
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Posts: 730
johnnyrvf Offline
BritBike Forum member
johnnyrvf  Offline
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Joined: Aug 2006
Posts: 730
Dordogne, SW France
Ahhh thanks Dave , I understand now ; OK ,all the original rubbers appear to be in very good condition the exception being the larger rubber bushes did'nt sit square in the tube and have taken a "set" , I shall replace these , the teflon spacers are marked around their perimiters although there were NO shims when I stripped the mounting down , the bike had failed it's M O T because of too much play in the iso's and the owner has left it for 15 years...... :rolleyes: I think someone had tried to set up the system but did'nt get it right , however they left it all nicely greased and unbodged so it's a pleasure to work on. Johnny smile


What d'ya mean it won't rev to 10?
1965 BSA A65D Lightning Rocket
1976 K*w*s*ki Z900.
1978 Triumph Bonn3ville (930 T160 Powered T140)
1988 H*nd* RC30
1990 Moto Guzzi California 3
1993 Y*m*h* TDM 850

Moderated by  Dave Comeau 


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